Paramagnetic defect centres in crystalline Alq<sub>3</sub>

Grecu, Maria Nicoleta; Mirea, Anisoara; Ghica, C.; Cölle, Michael; Schwoerer, M.

doi:10.1088/0953-8984/17/39/012

Cited by 17 publications

(22 citation statements)

References 33 publications

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“…Electron paramagnetic resonance (EPR) measurements on tris(8-hydroxyquinolinato) aluminium (Alq 3 ) show a signal consistent with a quasifree electron. Although the unstructured nature of the signal does not allow us to assess the magnitude of the two interactions, the observed anisotropy in the g factor is compatible with the presence of a weak SO interaction [24]. Furthermore, it has been pointed out that the g factor deviation comes from spin mixing between different orbital states, but does not include contributions from the spin mixing within the same orbital.…”

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confidence: 90%

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

et al. 2013

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Despite the great interest organic spintronics has recently attracted, there is only a partial understanding of the fundamental physics behind electron spin relaxation in organic semiconductors. Mechanisms based on hyperfine interaction have been demonstrated, but the role of the spin-orbit interaction remains elusive. Here, we report muon spin spectroscopy and time-resolved photoluminescence measurements on two series of molecular semiconductors in which the strength of the spin-orbit interaction has been systematically modified with a targeted chemical substitution of different atoms at a particular molecular site. We find that the spin-orbit interaction is a significant source of electron spin relaxation in these materials.

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confidence: 90%

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

et al. 2013

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“…Furthermore, the electron paramagnetic resonance line intensity in Alq 3 exhibits a similar step-like increase below 40 K (ref. 29).…”

Section: Quantitative Analysismentioning

confidence: 99%

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

et al. 2008

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Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.R ecently great efforts have been undertaken to use the spin degree of freedom in electronic devices. These activities are fuelled by the potential prospects of spin-electronic (or 'spintronic') devices for example in terms of increased processing speed and integration, non-volatility, reduced power consumption, multifunctionality and their suitability for quantum computing 1 . The most common method for using the spin in devices is based on the alignment of the electron spin ('up' or 'down') relative to either a reference magnetic field or the magnetization orientation of a ferromagnetic layer. Device operation normally proceeds with measuring a quantity such as the electrical current that depends on how the degree of spin alignment is transferred across the device. The so-called 'spin valve' is a prominent example of such a spin-enabled device that has already revolutionized hard-drive read heads and magnetic memory 1 . The efficient transfer of spin polarization in real device structures remains one of the most difficult challenges in spintronics, because it is dependent on more than just the properties of the individual materials that comprise the device.Recently 2,3 , the use of organic materials in spintronics has become of significant interest, primarily owing to their ease and small cost of processing and electronic and structural flexibility. Furthermore, the extremely long spin coherence times found in organic materials offer considerable advantages over other materials 3 . This favourable property is related to two factors, first the weak spin-orbit coupling of light elements such as carbon and second to the small nuclear hyperfine interaction 4,5 . The latter arises because the electron transport in π-conjugated molecules is normally confined to molecular states, delocalized to the carbon rings, the predominant isotope of which, 12 C, has zero nuclear spin 4 .A common way to measure spin diffusion is based on time-resolved optical techniques, where spin-polarized charge carrie...

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“…38 The applied magnetic field has to be at least as strong as those intrinsic to the material (e.g. the hyperfine field) 2 for the Hanle effect to unfold.…”

Section: Introductionmentioning

confidence: 99%

Hanle effect missing in a prototypical organic spintronic device

Riminucci

Prezioso

Pernechele

et al. 2013

Applied Physics Letters

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We investigate spin precession (Hanle effect) in the prototypical organic spintronic giant magnetoresistance (GMR) device La 0.7 Sr 0.3 MnO 3 (LSMO)/tris(8-hydroxyquinoline)(Alq3)/AlOx/Co. The Hanle effect is not observed in measurements taken by sweeping a magnetic field at different angles from the plane of the device. As possible explanations we discuss the tilting out of plane of the magnetization of the electrodes, exceptionally high mobility or hot spots. Our results call for a greater understanding of spin injection and transport in such devices.

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Paramagnetic defect centres in crystalline Alq₃

Cited by 17 publications

References 33 publications

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Hanle effect missing in a prototypical organic spintronic device

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Paramagnetic defect centres in crystalline Alq3

Cited by 17 publications

References 33 publications

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

Importance of Spin-Orbit Interaction for the Electron Spin Relaxation in Organic Semiconductors

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Hanle effect missing in a prototypical organic spintronic device

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Paramagnetic defect centres in crystalline Alq₃